1. Field of the Invention
The present invention relates generally to assembly line processing of electronic devices, and more particularly to automated transport of electronic devices under power for testtng during assembly line processing.
2. Description of the Prior Art
Electronic devices (e.g., computers, electronic tablets, cellular phones, smartphones, and appliances are mass-produced through assembly line processing. This assembly line processing is largely automated, with one important exception: testing of the electronic devices.
Testing of these electronic devices is a challenging issue because the testing needs to be performed in an environment shielded from electromagnetic interference. Interference from electromagnetic radiation (also known as radiofrequency (RF) inference can interrupt, obstruct, or otherwise degrade or limit the effective performance of electronic circuits, resulting in inaccurate test results. One way to control this problem is to test electronic devices in an RF chamber such as a Faraday cage or an RF shielded chamber.
An RF chamber is an enclosure formed from a conducting material (e.g., copper) or a mesh of the conducting material. A static electrical field outside the RF chamber causes electrical charges within the cage walls of conducting material to redistribute so as to cancel the electrical field's effects within the interior of the chamber. Thus, by intercepting the external electrical fields, the RF chamber shields the interior of the chamber from exterior electromagnetic radiation.
RF chambers are typically designed as either benchtop lab units or as room-sized chambers. Regardless of the type, the interior of the RF chamber must be completely enclosed—that is, sealed off from the external environment—to reap the benefit of protection from electromagnetic interference. RF chambers used in laboratory settings are typically accessed through one hinged door. A door opening (i.e., frame) in the RF chamber, however, breaks the RF shielding around the chamber, thereby allowing electromagnetic fields to penetrate the chamber through the opening. In an attempt to block electromagnetic fields from entering the RF chamber through the opening, a gasket interface is typically inserted between the door and the door opening of the chamber. The gaskets used in non-military settings typically shield up to about 60-80 dB at e.g., up to 4 GHz reliably. One problem with these RF chambers is that the gasket interface, subject to repeated wear and tear as the door is opened and closed, is a weak point in the RF shielding which can require frequent maintenance and/or replacement. Military modifications of the typical laboratory RF chamber have achieved a higher attenuation (shielding in excess of 100 dB at, e.g., 6 GHz) by replacing the gasket interface with a reed interface comprised of individual reeds typically made of copper. As with the gasket interface, however, the reeds break easily, and therefore need to be replaced frequently to maintain acceptable shielding.
One consequence of the necessity for completely sealing the RF chamber is that assembly line conveyors (typically comprising metallic components) cannot carry electronic devices into the cage for testing without disrupting the efficacy of the shielding. Maintenance and cost issues associated with maintaining effective RF shielding around current RF chamber doors, moreover, make more than one door into the chamber impractical—and thus make running a conveyor through (e.g., in one side and out another side of) the chamber impractical as well. Thus, although electronic devices are assembled on automated assembly lines, a device is typically removed from the automated assembly line for testing (e.g., RF), transported manually into an RF chamber, powered on, and then tested. After testing, the electronic device is powered down, manually removed from the RF chamber, and manually repositioned on the assembly line. The procedure becomes even more time-consuming and difficult if the electronic device being manufactured is large, heavy, and/or bulky (e.g., a desktop computer such as the iMac from Apple, Inc.) such that one worker can move only one device at one time. This cumbersome process slows production and increases the cost of manufacturing electronic devices. What is needed is a way to automate transport of an electronic device in a powered-on state from the automated assembly line into an RF isolated chamber for testing (e.g., RF) and out of the chamber and back to the automated assembly line after testing.